In a plasma processing apparatus that etches a film on a substrate, a focus ring is provided to surround the substrate in order to increase uniformity (etching uniformity) of a pattern in a surface of the substrate (for example, Patent Documents 1 and 2). Since the focus ring is etched and eroded by plasma as time passes by, the uniformity of the pattern in the surface of the substrate is decreased. Therefore, the focus ring is regularly replaced according to a using time thereof.
Patent Document 1: Japanese Patent Laid-open Publication No. 2008-078208
Patent Document 2: Japanese Patent Laid-open Publication No. 2003-229408
However, the focus ring is replaced without monitoring an erosion state of the focus ring. For this reason, the focus ring may be replaced even when it is still usable, or the focus ring may not be replaced even when it is badly eroded.